1. Field of Invention
This invention relates to maintenance stations for ink jet printing apparatus.
2. Description of Related Art
Fluid ejection systems, such as ink jet printers, have at least one fluid ejector head that directs droplets of fluid towards a receiving medium. Within the fluid ejector head, the fluid may be contained in a plurality of channels. Energy pulses are used to expel the droplets of fluid, as required, from orifices at the ends of the channels.
In a thermal fluid ejection system, such as a thermal ink jet printer, the energy pulses are usually produced by resistors. Each resistor is located in a respective one of the channels, and is individually addressable by current pulses to heat and vaporize fluid in the channels. As a vapor bubble grows in any one of the channels, fluid bulges from the channel orifice until the current pulse has ceased and the bubble begins to collapse. At that stage, the fluid within the channel retracts and separates from the bulging fluid to form a droplet moving in a direction away from the channel and towards the receiving medium. The channel is then re-filled by capillary action, which in turn draws fluid from a supply container. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. 4,849,774, incorporated herein by reference in its entirety.
A carriage-type thermal ink jet printer is described in U.S. Pat. No. 4,638,337, incorporated herein by reference in its entirety. That printer has a plurality of printheads, each with its own ink tank cartridge, mounted on a reciprocating carriage. The channel orifices in each printhead are aligned perpendicular to the line of movement of the carriage. A swath of information is printed on the stationary receiving medium as the carriage is moved in one direction. The receiving medium is then stepped, perpendicular to the line of carriage movement, by a distance equal to or less than the width of the printed swath. The carriage is then moved in the reverse direction to print another swath of information.
The fluid ejecting orifices of a fluid ejector head need to be maintained, for example, by periodically cleaning the orifices when the fluid ejection system is in use, and/or by capping the fluid ejector head when the fluid ejection system is out of use or is idle for extended periods. Capping the fluid ejector head is intended to prevent the fluid in the fluid ejector head from drying out. The cap provides a controlled environment to prevent fluid exposed in the nozzles from drying out.
A fluid ejector head may also need to be primed before initial use, to ensure that the fluid ejector head channels are completely filled with the fluid and contain no contaminants or gas bubbles. After significant amounts of ejecting, and at the discretion of the user, an additional but reduced volume prime may be used to clear particles or gas bubbles that can cause defects in the ejected swath of information. Maintenance and/or priming stations for the printheads of various types of ink jet printers are described in, for example, U.S. Pat. Nos. 4,364,065; 4,855,764; 4,853,717 and 4,746,938, while the removal of gas from the ink reservoir of a printhead during printing is described in U.S. Pat. No. 4,679,059, each incorporated herein by reference in its entirety.
The priming operation, which usually involves either forcing or drawing fluid through the fluid ejector head, can leave drops of fluid on the face of the fluid ejector head. As a result, fluid residue builds up on the fluid ejector head face. This fluid residue can have a deleterious effect on the quality of the ejected swath of information. Material from the receiving medium and other foreign material can also collect on the fluid ejector head face while ejecting fluid. Like the fluid residue, this foreign material can also have deleterious effects on the quality of the ejected swath of information.
The 717 patent discloses moving a printhead across a wiper blade at the end of a printing operation so that dust and other contaminants are scraped off the orifice before the printhead is capped, and capping the printhead nozzle by moving the printer carriage acting on a sled carrying the printhead cap. This eliminates the need for a separate actuating device for the cap. The 938 patent discloses providing an ink jet printer with a washing unit which, at the end of the printing operation, directs water at the face of the printhead to clean the printhead before it is capped.
This invention provides a cam-activated lever capping arm for a maintenance station for a fluid ejector head that carries and actuates one or more caps movably mounted on a cap carriage to cap the fluid ejector head nozzles.
In one exemplary embodiment of the maintenance station according to this invention, one or more caps are mounted on a translatable carriage and moves with the carriage. When the fluid ejection system is ejecting fluid, the translatable carriage is located in an ejection zone, where the one or more fluid ejector heads can eject fluid onto a receiving medium. When the fluid ejection system is placed into a non-ejection mode, the translatable carriage can be translated to the maintenance station located outside and to one side of the ejection zone. Once the cartridge is translated to the maintenance station, various maintenance functions can be performed on the one or more fluid ejector heads of the fluid ejection system depending on the rotational position of a cam shaft in the maintenance station. The cam shaft rotates in one direction, such as, for example, counterclockwise, to engage and drive the hardware that in turn operates the individual maintenance functions.
Rotating the cam shaft activates various maintenance mechanisms of the maintenance station, including a cap carriage. After the one or more fluid ejector heads arrive at the maintenance station, a vacuum pump is energized, and the cap carriage is elevated to the position where the one or more caps engage the one or more fluid ejector heads. The one or more caps are mounted on the cap carriage in a capping location. The fluid ejector heads are primed when a pinch tube mechanism opens one or more pinch tubes connected to the one or more caps. Opening the pinch tubes releases negative pressure created by the vacuum pump. In response, fluid is drawn from the one or more fluid ejector heads into the one or more caps.
The vacuum pump is then deenergized, while the cap carriage remains in position so that the one or more caps cap the one or more fluid ejector heads awaiting the ejection mode of the fluid ejection system. Thus, the one or more fluid ejector heads remain capped at the maintenance station until the fluid ejection system is placed into the ejection mode.
These and other features and advantages of this invention are described in or are apparent from the detailed description of various exemplary embodiments of the systems and methods according to this invention.